1. Field of the Invention
The present invention is generally related to a gear shift mechanism for a marine propulsion system and, more specifically, to a synchronizer device which allows toothed surfaces of independent rotatable components to be synchronized prior to meshing their two toothed surfaces together.
2. Description of the Prior Art
Many different types of gear shift mechanisms are well known to those skilled in the art of marine propulsion systems. In certain outboard motors, it is common to provide an axially slidable toothed mechanism which can be moved to engage either a forward gear or a reverse gear. The toothed mechanism is commonly referred to as a "dog clutch" and is used on many different styles of outboard motors to allow the operator to select either a forward or reverse gear.
In certain stem drive systems, friction surfaces of clutches are used to connect a driveshaft to an output shaft. In one particular type of stem drive gear shift mechanism, the friction surfaces are formed in the shape of frustums of cones. The clutch mechanism is moved axially to engage either of the two friction surfaces of the clutch with associated cone shaped surfaces on forward and reverse gears. This particular type of system will be described in greater detail below in conjunction with FIG. 1.
U.S. Pat. No. 4,244,454, which issued to Bankstahl on Jan. 13, 1981, discloses a cone clutch mechanism which has its forward and reverse clutch gears supported by bearings mounted on the housing, with a main shaft supported by bearings mounted on the housing in the same planes as the forward and reverse gear bearings. The male cone member is biased by two springs which each encircle cam faces on the member and bear against the forward and reverse clutch gears, respectively, in order to bias the cone member away from its center or neutral position.
U.S. Pat. No. 4,257,506, which issued to Bankstahl on Mar. 24, 1981, describes a shifter linkage for a cone clutch. A male cone member of a cone clutch mechanism has two springs, each encircling cam faces on the male cone member and bearing against the forward and reverse clutch gears, respectively, in order to bias the cone member away from its center or neutral position toward either the forward or reverse clutch gear. An eccentric motor on the shift actuator shaft engages with a circumfential groove in the male cone member to provide a vibrating force against the member for shifting. The shift means uses a cam and belt crank mechanism to convert axial movement of the shift controller to rotary movement of the actuator shaft.
U.S. Pat. No. 4,630,719, which issued to McCormick on Dec. 23, 1986, discloses a torque aided pulsed impact shift mechanism. The cone clutch sleeve on a main shaft is moved axially between forward and reverse counter-rotating gears by a yoke having mirror-image oppositely tapered cams on opposite sides thereof which are selectively rotatable to engage eccentric rings on the forward and reverse gears. This engagement drives the yolk away from the one engaged gear and toward the other gear to, in turn, drive the clutch sleeve out of engagement with the one gear such that torque applied through the cam-engaged gear ring assists clutch disengagement with the one gear such that requisite shift force decreases as speed and torque increases. The eccentric face surface of each ring actuates the yolk and drives the sleeve member out of engagement with the one gear and into engagement with the other with a pulsed impact hammer effect due to the eccentricity of the face surface as it rotates in a circumfential plane about the main shaft.
U.S. Pat. No. 4,869,121, which issued to Meisenburg on Sep. 26, 1989, describes a marine propulsion unit with an improved driveshaft arrangement. The marine propulsion unit is provided wherein the main drive shaft includes an integrally formed annular portion of enlarged diameter at the location of a previously utilized lower groove and tapers. The enlarged diameter portion increases the mass and strength of the shaft at a position which is subject to substantial torque forces, thus substantially eliminating problems of shaft fracture or breakage. In addition, the enlarged diameter portion is formed in the shape of a thrust collar so that the shaft can be accommodated by the previous known shaft mounting element without redesign of the latter.
U.S. Pat. No. 4,679,682, which issued to Gray et al on Jul. 14, 1987, discloses a marine drive shift mechanism with a detent canister centered neutral. The marine drive is provided with a shift mechanism including a detent canister assembly. A cylindrical canister contains a ball biased by a pair of concentric springs into engagement with the shifter level arm to center the latter into a neutral position. The canister assembly is a self contained modular unit inserted into the marine drive housing. The cylindrical canister has a left end wall with an aperture therethrough and has an open right end containing the ball. The first spring bears at its right end against the ball and extends axially leftward through the aperture in the left end wall of the canister and bears at its left end against the housing. The second outer concentric spring bears at its right end against the wall and is entirely within the canister and bears at its left end against the left end wall of the canister. Upon axial leftward depression of the ball by the shift lever arm, the first inner spring compresses a canister moves axially leftwardly until the left wall of the canister strikes the housing wall to close a tolerance-accommodating gap, whereby both springs compress during leftward compression of the ball.
Known marine shift mechanisms typically fall into one of two primary categories. In one type, the torque is transmitted from the output shaft of an internal combustion to a propeller shaft through a clutch mechanism which relies on friction between mating surfaces to transmit all of the torque from the engine to the propeller of the marine propulsion system. In another type, the marine propulsion system utilizes a total meshing relationship between gears to transmit torque from an internal combustion engine to a propeller shaft. However, this latter mechanism occasionally presents difficulty in shifting from neutral to either forward or reverse gear because of the significantly different speeds between the driveshaft and propeller shaft during the gear shifting procedure. Since the drive gear and output gear are not synchronized, significant impact can occur to the components of the system when a stationary gear is forced into meshing relation with a rapidly rotating gear. It would be therefore be significantly beneficial if a marine propulsion system could be developed in which a synchronizer matches the speeds of a drive gear and an output gear prior to forcing the tooth surfaces of the two gears into meshing relation with each other. It would also be significantly beneficial if the synchronizer is capable of providing a preselected degree of synchronization between rotating parts prior to meshing of gear teeth of those rotating parts. In other words, it would be beneficial if the synchronizer can be specifically designed to provide a preselected degree of synchronization prior to the gear tooth meshing procedures.
The patents described hereby are explicitly incorporated by reference in this description.